1. Field of the Invention
This invention relates to a photosensitive resin.
2. Description of the Prior Art
As photosensitive resins with high sensitivity, photosensitive resins having an azido group as a photosensitive functional group have been used, such as a photosensitive resin comprising the mixture of a non-photosensitive polymer and a bisazido type photo crosslinking agent disclosed in Published Unexamined Japanese Patent Application No. Sho 64-13540 and a photosensitive polymer comprising at least two azido groups in a molecule disclosed in Published Unexamined Japanese Patent Application No. Hei 4-50205.
However, since the former photosensitive resin comprises only two photosensitive functional groups in a molecule of the bis-azido type photo crosslinking agent, the resin has low photo crosslinking efficiency and sensitivity to light.
The latter photosensitive resin has an azide group and a sulfonate group directly bonded to an aromatic ring and also has a group of a carbon-carbon double bond conjugated with the aromatic ring. Therefore, sulfonate groups are associated with each other in a coating film formed from the photosensitive resin. As a result, many coupling reaction products (azo type conjugated compounds) are generated due to the coupling reaction between the azido groups near the sulfonate groups, and thus they absorb light useful for a reaction and prevent the inside of the coating film from curing. In other words, the strength of the coating film is not sufficient for practical usage.